Hi,
Do a search on the youtube.
You will find several instructions, it slightly different depending on the year of your 5.

For anyone who cares to know specifically about the MK1, but needs the answer to these questions in the future....

1) you have to slide the second console (around the handbrake back -
a. which involves taking two screws out from the rear left and right side (behind face plugs)
b. take out two screws at the front near the bottom of the seat slides (left and right - behind plugs).
c. remove the screws and covers then give a firm tug towards the back of the car to release the console
2) Once removed, try to sdlide the centre console back into place, I had to pivot from the bottom to get it to fit and reduce the amount of colliding between the centre console and the side panels (steering wheel cowling and the glovebox)
3) snap the cowling back into its original position

With regards the headunit installation, some companies will sell a cage which rests the entire weight of the unit on the inner edges of the double din gap, which can overstress the fascia and leave the headunit it in a state of reduced security. In the end, I removed the mount cage from the original factory unit, wedged placed it in the gap in the correct orientation, then mount the facia infront and the position it rests in on the rear stereo support mounts and the top of the heating controls and remains steady entirely without rattles.